Pacemakers, cardiac defibrillators, neurostimulators, and other implantable medical devices of a variety of shapes, sizes, and configurations have been developed over recent decades. In general, many such implantable medical device designs contain a main hermetically sealed body portion which generates pulses or signals, one or more leads for delivering these transmissions to a desired location, and a header assembly which serves as an intermediary portion for connections between the leads and the main sealed body portion.
In these designs, the main body portion is a sealed member having a housing made of implantable material. Interior components sealed in the main body portion may include a battery, electronic circuits, and other electrical components with only feed-through terminals passing to the outside of the sealed housing for connection with the header.
The leads of these devices are known to vary depending upon their specific desired application. In general, these leads are simply flexible wires coated in insulation that connect a medical device to a location in the body, such as the interior of the heart where wire leads are exposed. For example, leads have been used with a defibrillator and corresponding header for sensing information and delivering stimulation and shock therapy to chambers or appendages of the heart.
Header assemblies typically have been made of plastic or cast epoxy and have been necessary for receiving leads and connecting the leads to the electronic circuitry of the main body portion of a medical device. It is well-known that it is extremely important for leads and wires of an implanted header to avoid contact with fluids or substances which might disrupt or prevent use.
Such headers have typically comprised a small, flat housing compartment made of a plastic casing of partially rounded periphery which integrally fits in a recess adjacent the main body portion of the medical device. Headers also have included openings into which leads may be inserted and retained. Within these openings are contacts for receiving and delivering signals. Often these contacts are welded to conductor wires, contact blocks, and rings by the manufacturer assembling the header and main body of the medical device in a labor intensive procedure. A design which would not require such labor intensive procedure has been sought after in the medical device industry.
Leads placed in the openings of the header housing have almost universally been held in position by one or more set screws. Such set screws were inserted through small holes in the header housing to engage the outer perimeter of the leads from locations on the top or side of the header casing. The seal plug cavities are generally backfilled with silicone, epoxy, or other material in an effort to prevent leaks and avoid unwanted material contact with the screw threads or leads. Unfortunately, these measures have not been entirely effective and significant opportunities for leaks and failures were made possible when using set screws in this manner. A device which eliminates such set screws and passages has long been desired.
In prior designs, seal plug cavities were required to be made according to extremely close tolerances. If not properly made, seal plug cavities often became locations where leak paths were possible. Moreover, bonding septum plugs into the seal plug cavities was required by a user after initial manufacture. This often caused concerns about labor requirements and reliability. There has clearly been a desire to eliminate this difficulties in manufacturing and molding seal plug cavities.
Further, in many prior headers designs, numerous wire channels had to be molded or formed in the outer surface of the header body. Not only was this often a difficult task, but wires placed in such channels had to be backfilled with silicone, epoxy, or other material. This backfilling provided yet another location for potential failures of the connections within the medical device to occur. A header which would improve upon these features which are susceptible to failure has long been desired in the industry.
Therefore, a header for an implantable medical device is desired which provides greater reliability, less labor during and after initial manufacture, the elimination of potential leak paths and enhanced overall safety and performance.